Big hole drilling bit

ABSTRACT

An improved large diameter hole drilling bit consisting of a cutter head with a plurality of yokes fixedly mounted on the cutter head and a like plurality of roller cutters each rotatably mounted on a yoke. The drilling bit is adapted to be supported by a drilling rod which is rotated by a power unit of the drilling machine. During drilling operation, the cutter head is rotated about the axis of the drilling bit and at the same time the roller cutters are rotated about their own axes with respect to the yokes by contact to the rock or the like. Each roller cutter includes a load pin supported by the yoke fixed on the cutter head, a cutter cone having cutting teeth or individually replaceable tips thereon and bearing balls and/or rollers interposed between the cutter cone and the load pin so that the cutter cone is supported for free rotation on the load pin. Pressure-responsive seals and dust filters prevent foreign material from passing into the bearings. The load pin, cutter cone and bearing are preferably held in permanent assembly.

United States Patent [72] Inventor Hiroyasu Motoyama Tokyo, Japan [21]Appl. No. 873,266

[22] Filed Nov. 3, 1969 [45] Patented [73] Assignee Oct. 12, 1971 KokenSisui Kogyo Kabushiki Kaisha Tokyo, Japan [32] Priority Dec. 24, 1968 [33] Australia [31] Y 48341/68 [54] BIG HOLE DRILLING BIT 22 r a 44 14 z24 3,216,513 1 1/1965 Robbinset a1.

Primary Examiner-Ian A. Calvert AttorneyStevens, Davis, Miller & MosherABSTRACT: An improved large diameter hole drilling bit consisting of acutter head with a plurality of yokes fixedly mounted on the cutter headand a like plurality of roller cutters each rotatably mounted on a yoke.The drilling bit is adapted to be supported by a drilling rod which isrotated by a power unit of the drilling machine. During drillingoperation, the cutter head is rotated about the axis of the drilling bitand at the same time the roller cutters are rotated about their own axeswith respect to the yokes by contact to the rock or the like. Eachroller cutter includes a load pin supported by the yoke fixed on thecutter head, a cutter cone having cutting teeth or individuallyreplaceable tips thereon and bearing balls and/or rollers interposedbetween the cutter cone and the load pin so that the cutter cone issupported for free rotation on the load pin. Pressure-responsive sealsand dust filters prevent foreign material from passing into thebearings. The load pin, cutter cone and bearing are preferably held inpermanent assembly.

PATENTED um I 21971 sum 1 nr 3 FIG. I

FIG. 2

INVENTOR ATTORNEY PATENTEBucnzm: 3612.197 sum 2 or 3 INVENTOR ATTORNEYBIG HOLE DRILLING BIT The present invention relates to a drilling bitfor excavating a big hole or large diameter hole in rock or the like.

The big hole, drilling bit consists of a cutter head, a plurality ofyokes fixedly mounted on said cutter head and roller cutters eachrotatably mounted on each of said yokes. The drilling bit is adapted tobe supported by a drill rod which is rotated and propelled by a powerunit of a drilling machine. During the drilling operation the cutterhead is rotated on an axis of the drilling bit and at the same time theroller cutters are rotated on their own axes on the respective yokes bycontact with the rock or the like.

In general the roller cutter includes a load pin supported by the yokefixed on the cutter head, a cutter cone having cutting teeth or tipsthereon and bearing balls and/or rollers interposed between said cuttercone and said load pin, whereby the cutter cone is supported on the loadpin so as to be freely rotatable thereon. The load pin, the cutter coneand the bearing balls and/or rollers are usually held in permanentlyassembled relationship.

In such roller cutter wear is produced mainly on the two portions,namely on the cutting portion and on the bearing portion. However thedegrees of wear on the two portions are different from each other, andbefore the wear on one of these portions has become excessive the rollercutter must be removed from the cutter head as a whole and replaced by anew one. It has been experienced that more wear is produced on thebearing portion than on the cutting portion, and consequently, if thewear on the bearing portion has reached a predetermined degree theentire roller cutter should be replaced by a new one even if the cuttingportion is still usable. This is uneconomical in view of the fact thatthe cutting teeth or tip are very high in cost and usually occupy about60 to 70 percent of the cost of the entire roller cutter.

It has been proposed to provide a construction of a roller cutterassembly in which a load pin, a cutter cone and a bearing can bedisassembled so that only the cutter cone can be replaced by a new one.In such a construction, however, if a bearing surface or an insidesurface of the cutter cone has been worn the cutter cone should bereplaced by a new cutter cone even if the cutting portion is stillusable.

Accordingly it is an object of the present invention to provide adrilling bit which eliminates the above disadvantages in the rollercutter.

It is an object of the present invention to provide a drilling bit whichcan reduce running cost of drilling.

It is another object of the present invention to provide a drilling bitin which a roller cutter is constructed from components which can beeasily assembled and disassembled.

It is a further object of the present invention to provide a drillingbit in which a roller cutter is constructed from components each ofwhich can be easily replaced by a new component without requiringreplacement of the roller cutter as a whole.

It is another object of the present invention to provide a drilling bitin which a roller cutter includes a bearing assembly which can be easilyremoved and replaced by a new one without requiring replacement of acutter cone.

It is another object of the present invention to provide a drilling bitin which a roller cutter includes a bearing assembly the wear of whichis reduced to minimum by preventing foreign material from entering intothe bearing assembly.

It is a further object of the present invention to provide a drillingbit in which a roller cutter comprises cutter tips which can be easilyremoved and replaced by new ones.

In accordance with the present invention there is provided a drillingbit for excavating a big hole, comprising a cutter head, a plurality ofyokes fixedly mounted on said cutter head and roller cutters eachrotatably supported on each of said yokes, each of said roller cutterscomprising a load pin supported by said yoke, a bearing assemblyincluding a pair of aligned inner races mounted on said load pin, anouter race and a set of bearing rollers and bearing balls locatedbetween said inner races and said outer race, and a cutter cone fixed onsaid outer race and having cutting portions thereon, said load pin,inner races, outer race, bearing rollers and balls and cutter cone beingdetachably assembled together to form the roller cutter.

Further in accordance with the present invention there is provided adrilling bit of the above kind, in which the cutter cone has a pluralityof cutter tips which can be easily removed and replaced.

Now the invention will explained in detail with reference to thedrawings which illustrate embodiments of the present invention in which:

FIG. 1 is a side view of the drilling bit according to an embodiment ofthe present invention;

FIG. 2 is a sectional view, in enlarged scale, showing one cutterroller;

FIG. 3 is an exploded sectional view of the roller cutter shown in FIG.2;

FIG. 4 is an enlarged sectional view of a part of FIG. 2;

FIG. 5 is a sectional view similar to FIG. 2 showing a modified form ofthe present invention; and

FIG. 6 is a fragmentary sectional view showing a modification of thecutting tip shown in FIG. 5.

Referring to the drawings, the drilling bit generally indicated by 10comprises a cutter head having a plurality of stages 12, yokes l4fixedly mounted on the respective stages of said cutter head and rollercutters 16 each rotatably supported by each of said yokes. The drillingbit as shown in FIG. 1 is adapted to be connected by conventionalcoupling means 18 to a drill rod (not shown) and rotated and driven intothe rock or the like.

' Each roller cutter 16 comprises a load pin 20 supported on the yoke 14and fixed thereon by a lockpin 22, a bearing assembly including pair ofaligned inner races 24 and 26 mounted on said load pin, an outer race 28and a set of bearing rollers 30 and 32 and bearing balls 34 locatedbetween said inner races and said outer race, and a cutter cone 36 fixedon said outer race 28. The cutter cone 36 shown in FIG. 2 has cuttingteeth 38 integrally formed thereon. Seals 40 are interposed between theouter race 28 and the inner races 24 and 26 of the bearing assembly atthe both ends thereof to prevent foreign material from entering into thebearing assembly. The outer race 36 has a flange 42 at its one end and aperipheral groove 44 at its other end (FIG. 3). A snapring 46 is fittedinto said peripheral groove 44, so that the cutter cone 36 is held onthe outer race 28 between the flange 42 and the snapring 46.

The load pin 20, inner races 24 and 26, outer race 28, bearing rollers30 and 32, bearing balls 34, cutter cone 36 and seals 40 are detachablyassembled together to form the roller cutter. When assembling the rollercutter, the cutter cone 36 is mounted on the outer race 28 and fixedthereon by the snapring 46 fitted in the peripheral groove 44, and theinner races 24 and 26 with the seals 40 and the bearing rollers 30 and32 and the bearing balls 34 are inserted into said outer race 28 fromthe both ends thereof. The assembled cutter cone and the bearingassembly are positioned in the yoke 14 and the load pin 20 is insertedand fixed by the lockpin 22. Thus the roller cutter is assembled andsupported on the yoke 14. The disassembly of the roller cutter can beeasily made by removing the lockpin 22, drawing the load pin 20 out ofthe yoke and then removing the inner races 24 and 26 and the outer race28 from the cutter cone 28.

The seal 40 consists of a dust filter 48 positioned on the axiallyoutermost end of the roller cutter and a pressure-responsive packing 50positioned axially inside of said dust filter 48 (See FIG. 4). The dustfilter 48 includes two layers of filter rings 52 and 54 held betweenmetal rings 56 and 58, one layer of filter ring 52 having concentricallyarranged two rings made of sealing material and the other layer 54having concentrically arranged three rings of the same material. Thepressureresponsive packing 50 consists of a ring of elastic materialhaving U-shaped cross section which opens toward the dust filter. Duringoperation, mud, small stones or other foreign material is prevented frompassing into the bearing assembly by the dust filter 48 and only fluidreaches to the pressureresponsive packing 50, which radially expands inresponse to the pressure of the fluid to tightly close the space betweenthe outer race and the inner race. Thus the seal 60 serves to seal thebearing assembly so as to prevent the foreign material from passingtherein which otherwise would increase the wear of the bearing assembly.

FIG. 5 shows a modified form of the present invention in which thecutting portion of the cutter cone 36 is formed by cutter tips made oftungsten carbide. In this form the cutter cone has a plurality ofradially extending holes 60 which pass through the cutter cone 36 frominside to outside and a plurality of cutter tips 62 inserted into eachof said radial holes 60. ln FIG. 5, each hole 60 is formed as a steppedhole having a shoulder 64 with which the bottom end of the cutter tip 62engages. Thus the shoulder 64 serves to receive the load acting on thecutter tip and hold the cutter tip at the fixed position. The hole 60may be made as a tapered hole as shown FIG. 6 which has a tapered wall66 reducing its diameter toward the inside of the cutter cone. A cuttertip 68 having a tapered wall corresponding to said tapered wall 66 isinserted into the tapered hole.

Thus the respective cutter tips, which have been worn, can be separatelyremoved and replaced by new ones, which eliminates the need forreplacement of the whole cutter cone. The cutter tip can be easilyremoved from the cutter cone by pushing the bottom end by a suitabletool passing through the hole from the inside of the cutter cone.

It will be understood from the above description that according to thepresent invention the roller cutter can be easily disassembled to therespective elements and any element which has been worn or damaged canbe easily replaced by a new one, without requiring the replacement ofthe whole roller cutter, so that a great economy can be obtained in therunning cost of drilling.

While the preferred embodiment of the present invention has beendescribed in detail with reference to the drawings, it

will be appreciated that the invention is susceptible to modification,variation and change without departing from the scope of the appendedclaims.

What is claimed is:

1. A drilling bit for excavating a large diameter hole comprising acutter head, a plurality of yokes fixedly mounted on said cutter headand a like plurality of roller cutters each rotatably supported on oneof said yokes, each said roller cutter comprising a load pin supportedat each end by said yoke, a bearing assembly and a cutter cone, saidhearing assembly comprising a pair of aligned inner races mounted onsaid load pin, an outer race, and a set of bearing rollers and ballslocated between said inner races and said outer race, said cutter conebeing fixedly mounted on said outer race of the bearing assembly andhaving a plurality of radially extending holes therein, said holeshaving tapered walls with the smaller diameter towards the inside of thecutter cone, a like plurality of cutter tips having a correspondinglytapered wall and being detachably mounted in said holes of the cuttercone, and means to detachably assemble said load pin, inner races, outerrace, bearing rollers and balls, and cutter cone together.

2. A drilling bit according to claim 1, in which said outer race of thebearing assembly has a flange at one end and a peripheral groove at theother end, a snapring detachably assembled in said peripheral groove tohold said cutter cone in position on the outer race between said flangeand said snapring.

3 A drilling bit according to claim 1, further comprising sealing meansfitted between the outer race and the inner race of the roller cutter ateach end thereof, each said sealing means comprising a dust filterpositioned at the axially outermost end of the roller cutter and apressure-responsive packing positioned axially inside of said dustfilter and adapted to radially expand in response to pressure passingthrough said dust filter.

1. A drilling bit for excavating a large diameter hole comprising acutter head, a plurality of yokes fixedly mounted on said cutter headand a like plurality of roller cutters each rotatably supported on oneof said yokes, each said roller cutter comprising a load pin supportedat each end by said yoke, a bearing assembly and a cutter cone, saidbearing assembly comprising a pair of aligned inner races mounted onsaid load pin, an outer race, and a set of bearing rollers and ballslocated between said inner races and said outer race, said cutter conebeing fixedly mounted on said outer race of the bearing assembly andhaving a plurality of radially extending holes therein, said holeshaving tapered walls with the smaller diameter towards the inside of thecutter cone, a like plurality of cutter tips having a correspondinglytapered wall and being detachably mounted in said holes of the cuttercone, and means to detachably assemble said load pin, inner races, outerrace, bearing rollers and balls, and cutter cone together.
 2. A drillingbit according to claim 1, in which said outer race of the bearingassembly has a flange at one end and a peripheral groove at the otherend, a snapring detachably assembled in said peripheral groove to holdsaid cutter cone in position on the outer race between said flange andsaid snapring. 3 A drilling bit according to claim 1, further comprisingsealing means fitted between the outer race and the inner race of theroller cutter at each end thereof, each said sealing means comprising adust filter positioned at the axially outermost end of the roller cutterand a pressure-responsive packing positioned axially inside of said dustfilter and adapted to radially expand in response to pressure passingthrough said dust filter.